I'm putting together a trip in my head down the Pacific Coast. I'm thinking of taking the train up to
Portland, OR then heading out to the the coast and down to SF (my home). A fairly typical Pac Coast tour.

My question is getting from Portland to the coast. I penciled out a route along the "SW Pacific Hwy" (that's what it's called on the map), which turns into Hwy 99W, then onto Hwy 18 and finally onto Hwy 22 to the coast. Looks nice on the map....

I just picked up "Bicycling the Pacific Coast" and it shows taking Hwy 26 to Cannon Beach.

Does anyone know the route I sketched out on the map? Does that route make sense or is there a better route from Portland to the coast?

Picking a straight line on a map can be very risky -
Primarily because most people driving do, too.
If the road has good shoulders, you will be fairly safe -
But have mondo traffic to deal with.
If there are no shoulders it will be a nightmare.

The three most important variables are -
1. Traffic volume
2. Shoulder width
3. Speeds

Obviously, we would all like to have the perfect road for cycling -
An empty road with great pavement and gentle grades.
Some variables mitigate others -
For ex. - if there is no traffic, you really don't need shoulders.
If traffic moves slowly, then curves are less of an issue.

If you really don't have to go to Portland, then Salem is a better destination on the train.
Salem has baggage service and is much easier to bike out of - maybe via Wheatland Ferry?
(Not to mention that you will be getting in in the afternoon in either Portland or Salem.)
Or, you can take the train to Portland and ride out to Manzanita via Scappoose, Mist and Jewell.
(South of US 26 you follow the Nehalem River on a Nehalem River Rd - mostly paved.)

I rode through Portland. I remember people trying to explain to me that escaping the city on bicycle was a bit difficult because of freeways and such, so I took the trolley train from downtown to the end of the line somewhere west of the city, Hilsboro station I think, and made my way down to HWY 18. I don't remember anything particular notable about the roads or traffic on the way so it couldn't have been terrible. Certainly not worse than the unshouldered heavy traffic climb through the redwoods after Crescent City, CA.

I started from Portland around noon and finished that day near Lincoln city. I slept on the beach there and made a little fire inside a hobo log hut. It might not be the greatest idea though because the beach can get pretty busy, especially on weekends, and also even if you are careful, sand gets into all the greased and lubed parts of your bicycle which took a long while to clean out. It also might be prohibited.

I rode out highway 30 (I think) from Astoria to Portland, about a hundred miles. It was pleasant. Not too much traffic but still some. The scenery is alright, I have had better and worse. Plus Astoria is at the Northern most part of the coast and a pretty little town.

I've cycled from numerous places in Oregon to the coast. We did it in reverse on a bike trip ending in Astoria last summer. Amtrack runs a bus between PDX and Astoria. The only hassle is the bike needs to be boxed to go on the bus. We had to box the bikes to go from PDX to Vancouver, BC; but he driver in Astoria let us put the bike on the bus unboxed (it was an early Sunday morning). If your bike is already boxed not a problem. Portland station sells boxes for $15. They are big boxes, and very little disassembly is required.

Good advice above. Hwy 30 is a good ride along the Columbia River. Salem to Lincoln City via of Highway 22-18 is a zoo, The Jewel turnoff from 26 to Astoria has light traffic, but is narrow with lots of curves, and log trucks.
We've ridden Hwy 20 from Albany to Newport and it is narrow but OK. There is a train station in Albany. My choices would be Hwy 30 or Hwy 20, if I was starting from a train station in the Willamette Valley.

I did this trip. I took Highway 30 out of Portland. I think the route was described in "Bicycling the Pacific Coast," although there was one place in Portland where the route wasn't quite right. I was riding through neighborhoods and the described road didn't go through. I had to go down a pedestrian path to get through. I remember that it was steep and slippery, but not a big deal.

Highway 30 was fine. I wanted to stop overnight halfway. I found a nice big park where the old Trojan nuclear power plant was. (The cooling tower was still there, though I think it has since been demolished.) But camping wasn't allowed. I've heard it might be allowed now. I stopped at a motel in Rainier right before the big bridge to Longview. It was cheap, with a nice Mexican restaurant across the street. There was no grocery store in town though; just a mini-mart at the Chevron station.

I've read on CrazyGuy journals that there is a small campground in the area with a few primitive campsites. Maybe Hudson-Parcher park?

I spent a layover day at Fort Stevens State Park before heading south.

This is one of my favorite routes - as much because of the number of bike tourers I met as anything.